Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Well beyond the destructiveHint/idempotentHint annotations: it discloses the free-plan refusal, that everyone sees a deletion indicator, that it is irreversible, and the ~15-minute caveat where WhatsApp may not actually delete for everyone. These are exactly the operational traits an agent needs to set expectations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Action, scope, and prerequisites are front-loaded in the first sentences, and the confirmation warning follows logically. The return-value enumeration of chat contact fields is dense, but with no output schema it is carrying the burden of explaining what comes back, so it earns its space.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Despite no output schema, the description fully specifies the return shape (message_id, status values, chat, warning, error) and explains when warning appears. Combined with the paid-plan, ownership, and revertibility constraints, nothing essential is missing for correct invocation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is already 100% and the single parameter is self-documented, so baseline is 3. The description adds real value by saying the chat is looked up automatically from the id and that the id comes from read_chat_history or search_messages, removing any doubt about needing a chat identifier.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a precise verb+resource (deletes a WhatsApp message) plus the scope that matters most — 'for everyone in the chat' — and clarifies it works in both 1:1 and group chats. This distinguishes it cleanly from siblings like edit_message or mark_as_read without needing to open a schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives explicit prerequisites: paid plan only, must be the user's own message (from 'Me'), and points to read_chat_history / search_messages for the id. It also specifies a confirmation policy before invoking. It stops short of naming the direct alternative tools (edit_message, react_to_message) for an agent weighing modification options.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.